XML 126 R90.htm IDEA: XBRL DOCUMENT v3.10.0.1
Income Taxes (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]          
Federal statutory income tax rate 21.00% 35.00% 21.00% 35.00% 35.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent (19.00%) (19.00%) (29.00%) (18.00%)  
State income tax, net of federal income tax benefit 1.00% (0.00%) (6.00%) (1.00%)  
Income tax effect of foreign income (0.00%) (3.00%) (3.00%) (4.00%)  
Effects of ratemaking (2.00%) (0.00%) (3.00%) (0.00%)  
Equity income 0.00% 1.00% 0.00% 1.00%  
Other, net 1.00% 1.00% 1.00% (0.00%)  
Effective income tax rate 2.00% 15.00% (19.00%) 13.00%  
Production Tax Credit Carryforwards [Abstract]          
Years eligible for federal renewable energy production tax credit     10 years    
Related Party Tax Expense [Abstract]          
Long-term income tax receivable $ (494)   $ (494)   $ 0
Parent Company [Member]          
Related Party Tax Expense [Abstract]          
Related party transaction, cash received for income taxes, net     450 $ 659  
Long-term income tax receivable $ 494   $ 494